1. Field of the Invention
The present invention relates generally to battery electrolyte level testing and, more particularly, to an external apparatus and methods to check battery electrolyte levels.
2. Description of the Prior Art
It is well known that a wide variety of machines, vehicles, and the like, utilize batteries with electrolyte levels that need to be periodically checked. In lead-acid batteries, during normal operation, sulfuric acid is not lost from the electrolyte of the battery. However, water is lost from the electrolyte due to evaporation and electrolysis during ventilation and charge operations.
The water needs to be replaced regularly to ensure that the electrolyte remains at a proper level. The required frequency for adding water may be determined by maintaining a close watch of electrolyte levels. If the battery electrolyte level is too low, the battery may be permanently damaged. When necessary, and if practical, water should be added before a charge operation, preferably before an equalizer. This procedure allows the water to mix with the electrolyte during the charge.
Checking the water level on batteries is time-consuming and potentially dangerous due to the need to open the battery caps, and look into the cells to see the level. Sulfuric acid fumes inhalation, spillage, explosions due to hydrogen production, and skin contact with acid are real dangers faced by sailors testing the water level on batteries.
The following United States patents describe various prior art systems that may be related to the above and/or other problems.
U.S. Pat. No. 4,280,126, issued Jul. 21, 1981, to White discloses an apparatus for locating the level of a liquid in a closed metallic container having curvilinear walls with a thickness of from ⅛ to ⅜ inch comprising a manually portable transducer having a piezoelectric material for transmitting and receiving sonic waves, and a sonic pulse generator capable of exciting the piezoelectric material to emit sonic signals into the container from a location adjacent the outside wall of such container at a frequency within about 20% of the natural resonate frequency of the container. The apparatus further includes the electronic circuitry necessary for determining that the reception of the sonic signals transmitted into the container is in balance when the transducer is at a location away from the interface of the fluids within the container, and the electronic circuitry necessary for determining the vertical location at which the reception of sonic signals transmitted into the container is no longer balanced as the transducer is manually moved toward the interface of the fluids.
U.S. Pat. No. 5,017,909, issued to May 21, 1991, to Goekler discloses a non-intrusive fluid level detector including a single point capacitive sensor mounted on the outside surface of a receptacle such that capacitive principles can be utilized to sense the level of a liquid contained within the receptacle. The sensor assembly is disposed in a substantially fixed position on the exterior wall of the receptacle wherein the dielectric effect of the liquid changes the effective capacitance of the sensing capacitor as the liquid rises and falls within the receptacle. This change in effective capacitance is detected by electronic circuitry included in the detector device. In one embodiment, the fluid level detector is directly mounted to a completely non-conductive receptacle. In another embodiment, the fluid level detector is mounted to a non-conductive window which is an integral part of a receptacle fabricated out of a conductive material.
U.S. Pat. No. 5,132,626, issued Jul. 21, 1992, to Limuti et al, discloses nonintrusive sensors capable of measuring various storage cell parameters such as voltage, state-of-charge, electrolyte level, internal resistance, and temperature are attached to a monitoring module which gathers and processes signals representative of information concerning the condition of electrolytic storage cells and transmits the information to a central computer for further processing. In response to commands issued by the central computer, appropriate maintenance and/or repair operations can be initiated. Alternatively, the system described can be used to automatically perform such maintenance tasks as checking and adding electrolyte levels, reducing the voltage in cells whose output voltage is too high, and leveling the state-of-charge of each cell in an array of electrolytic storage cells. The system can monitor other functions of the electrolytic storage cells, including the evolution of hydrogen gas and the accumulation of sediments in individual electrolytic storage cells.
U.S. Pat. No. 5,438,868, issued Aug. 8, 1995, to Holden et al, discloses a noninvasive ultrasonic liquid level indicator for indicating the level of a liquid in a reservoir which comprises an ultrasonic transducer assembly, structures for holding the transducer assembly in a dry coupled attachment with the reservoir at selectable locations against an exterior surface of the reservoir, and a monitor for revealing a change in liquid height. The transducer assembly conveys signals regarding changes in liquid height to a monitor which warns the user in time to add more liquid or replace the reservoir before the liquid supply “runs dry.” The manners for holding the assembly in place include, but are not limited to, a strap, a clamp, or adhesive material, such as tape. These manners allow the user to selectively place the transducer assembly along the reservoir at the desired triggering point.
U.S. Pat. No. 5,880,364, issued Mar. 9, 1999, to Dam discloses a non-contact ultrasonic system for measuring the volume of liquid in a container in which an ultrasonic sensor is disposed opposite the top of the container. A circuit provides pulses of ultrasonic energy for transmission through the air to the air-liquid interface of liquid in the container and for measuring the round trip transit time from the sensor to the interface and back to the sensor. A computer is programmed with dimensional data of the container internal volume and computes the volume of liquid in the container based on the dimensional data and the round trip transit time. The computed volume data is stored. The system can measure the volume of a plurality of containers using a plurality of sensors that are operated in sequence or at the same time or single sensor in which the plurality of sensors are moved relative to the single sensor for the volume of each of the sensors to be sequentially measured.
U.S. Pat. No. 6,227,053, issued May 8, 2001, to Purpura et al, discloses a sensor that emits a plurality of ultrasonic bursts. A rack of containers is transported under the sensor at a slew speed that allows the sensor to detect at least first and second echoes from each of the bursts. Data points, corresponding to each of the first and second echoes, are generated and the data points are captured in a memory device. The data points, generally reflecting the levels of the rack and any containers, are processed to dynamically and non-invasively (i.e., without physically contacting the liquid with a probe) determine information about the container types, whether any container is capped, and, if one or more containers are uncapped, the liquid level in the uncapped containers. This profiling may be used in a variety of devices and is particularly useful in a sample handler in an automated analytical instrument, where the ultrasonic sensor may be positioned above a rack transport mechanism.
U.S. Pat. No. 6,943,566, issued Sep. 13, 2005, to Florin et al, discloses a sensor which is applied to the wall of a container or is integrated into the wall. An alternating voltage is applied to the sensor in order to measure the level of the contents of the container, the capacitance or the electrical field produced being a measure for the fill level.
United States Patent Publication No. 2002/0083766, published Jul. 4, 2002, for Hongerholt et al, discloses a built-in test system for an ultrasonic liquid level sensor that includes a transducer assembly having an ultrasonic transducer, and a switch that will be actuated when the ultrasonic transducer is in intimate contact with a surface of a tank in which level is to be determined. Once the switch is actuated to indicate that the ultrasonic transducer is properly coupled to the surface, a test sequence is initiated to determine that the level of ultrasonic transmissions are above a certain desired threshold for a selected period of time, and after which the circuit looks for echoes to determine the depth of the liquid in the tank. Thereafter, the test sequence is repeated for each cycle of level sensing.
United States Patent Publication No. 2001/0015099, published Aug. 23, 2001, for Blaine, discloses a disposable sensor for non-invasively detecting and characterizing a container's contents. By generating microwave frequency signals, electromagnetic fields are produced by a sensor and penetrate a container. The EM fields are analyzed in regards to how they are perturbed by the container contents. Analysis of the perturbed EM fields enables determination of content level, content purity, content density, content temperature, container pressure, content conductivity, and the like.
U.S. Patent Publication No. 2007/0261487, published Nov. 15, 2007, for Sintes et al, discloses a level sensor for providing an indication of liquid level in a container comprising: an ultrasonic transducer for emitting an ultrasonic signal to the surface of the liquid and for detecting a return signal, reflected from the surface, a controller that instructs the transducer to emit ultrasonic signals and receives an indication that a return signal has been detected, the controller comprising a timer for measuring the time period between emission of the ultrasonic signal and receipt of a return signal, the determined time period providing an indication of the liquid level, and a radio transmitter that receives an indication of the liquid level and transmits a radio liquid level signal comprising the level indication to a remote output unit.
Extract from Japanese Patent No. 2000-5636041, discloses a supersonic sensor that is made to contact the outer surface of battery case. An ultrasonic wave is transmitted towards a battery case from an ultrasonic element of sensor. The magnitude of ultrasonic wave reflected from an inner surface of battery case is detected to judge liquid level inside battery case.
Extract from Japanese Patent No. 2000-205931, discloses a method to inspect the liquid level of a battery liquid by setting the size of an inside surface reflected wave generated in the first place on a boundary surface existing on an inside surface of a battery case as an evaluation index.
The above cited prior art does not disclose a suitable and transportable means to acoustically check battery electrolyte levels with micrometer accuracy without opening the cell caps. Consequently, those skilled in the art will appreciate the present invention that addresses the above and other problems.